1. Field of the Invention
Embodiments of the present disclosure relate to line terminals and, more particularly, to a line terminal and method for determining operational status of a U interface.
2. Description of Related Art
A user terminal is usually connected between an exchange terminal and a digital service unit through a line terminal in an integrated service digital network (ISDN). The user terminal and the digital service unit may be both disposed in a room, and communicate with each other via a U interface.
A working status of the user terminal depends on a communication status between the digital service unit and the line terminal, and a communication status between the digital service unit and the line terminal depends on a working status of the U interface connected between the line terminal and the exchange terminal. Thus, the working status of the U interface determines the working status of the user terminal. Generally, many factors, such as a synchronous time between the line terminal and the digital service unit, a loop polarity of the U interface, and an abnormality of the digital service unit, may affect the working status of the U interface. Therefore, it is very important to determine if the U interface works normally or abnormally in order to maintain operation of the ISDN.